Electrical stringed musical instrument



Aug. 22, 1939. R. DOPYERA ELECTRICAL STRINGED MUSICAL INSTRUIENT .www

Filed April 13, 1956 n 22, 1939. R. DOPYERA 2,170,294

ELECTRICAL STRNGED MUSICAL INSTRUIENT Filed A i 15, 1936 3 Sheets-Sheet 2 Aug. 22, 41939. R. DOPYERA 2,170,294

ELECTRICAL STIRINGED MUSICAL INSTRUIENT Filed April 13, 1936 3 Sheets-Sheet 3 95 Ha/@Jiang Patented Aug. 22, 1939 i UNITE STATES ELECTRC'AL STRNGED MUSEUM INSTRUMENT Rudolph Dopyera, Los Angeles, Calif.

Application April 13, i936, Serial No. 74,058

13 Claims.

This invention relates to stringed musical instruments and relates more particularly to electrical stringed musical instruments. A general object of this invention is to provide a simple, practical stringed musical instrument embodying an improved pick-up means.

Another object of this invention is to provide a stringed musical instrument embodying an improved pick-up which provides a concentrated magnetic field through vwhich the instrument strings pass so that vibration of the strings varies the reluctance ofthe magnetic circuit to induce a current in an -induction coil of the pick-up, which current may be suitably converted into clear sustained musical tones truly representative of the vibration of the strings and which may be made appreciably louder than the tones produced by ordinary stringed musical instruments.

Another object of this invention is to provide an electrical musical instrument of the character mentioned embodying a compact, novel and fully adjustable electro-magnetic pick-up means.

Another object of this invention is to provide an electrical musical instrument of the character mentioned in which the pick-up means may be easily and conveniently regulated or adjusted by the musican to provide for the production of tones of the desired quality, amplitude, etc.

Another object of this invention is to provide an electrical musical instrument of the character mentioned in which the only visible parts of the electro-magnetic pick-up unit are the adjusting knobs and the pole pieces of the magnet providing the concentrated magnetic field through which the strings pass,

Another object of this invention is to provide an electrical musical instrument of the kcharacter mentioned embodying an improved and simplifiedA pick-up comprising a relatively stationary magnet, a relatively stationary induction coil and shiftable adjustable magnet pole pieces engaging the poles of the magnet, passing through the coil and concentrating a non-uniformA magnetic eld about the vibratory instrument strings.

Another object of the invention is to provide a musical instrument of the character mentioned in which the adjustable magnetic pole pieces carry the magnetic influence to the several strings of the instrument whereby the pick-up means is responsive to vibration of any one or all of the strings.

Another object of this invention is to provide an electrical musical instrument of the character mentioned in which the adjustable magnetic pole pieces may be readily adjusted toward (Cl. 84-L16) and away from the series of instrument strings to a like or uniform extent to correspondingly increase or lessen the action of the several strings on the magnetic flux, or one pole piece may be adjusted relatively closer or farther away from its adjacent strings than the other pole piece to effect a greater or lesser action of certain of the strings on the magnetic llux.

Another object of this invention is to provide an electrical musical instrument of the character mentioned embodying novel means for adjusting the pole pieces and for maintaining the adjustable pole pieces in proper contact with the poles of the magnet.

A further object of the invention is to provide an improved electrical musical instrument of the character mentioned that is simple and inexpensive.

The various objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of the invention, throughout which description reference is made to the accompanying drawings, in which:

Fig. 1 is a plan elevation of one form of musical instrument provided by this invention. Fig. 2 is an enlarged fragmentary longitudinal detailed sectional View taken substantially as indicated by line 2 2 on Fig. 1. Fig. 3 is a fragmentary longitudinal or horizontal detailed sectional view taken substantially as indicated by line 3 3 on Fig. 2. Fig. 4 is a transverse detailed sectional view taken as indicated by line 4-4 on Fig. 3. Fig. 5 is a schematic Wiring diagram of the circuit embodied in the instrument illustrated in Figs. 1 to 4. Fig. 6 is a plan elevation of another embodiment of the invention. Fig. 7 is an enlarged transverse detailed sectional view taken substantially as indicated by line 1 1 on Fig. 6. Fig. 8 is a longitudinal fragmentary detailed sectional view taken as indicated by line 8-8 on Fig. 7. Fig. 9 is a fragmentary vertical detailed sectional View of a slightly modified form of the invention.

The present invention is adapted to be employed in stringed musical instruments of various characters. In the following disclosure I will describe theinvention embodied in two instruments of the guitar class; it being understood that the invention is not to be construed as limited or restricted to the specic forms or applications about to be described.

'Ihe form of the present invention illustrated in Figs. 1 to 5, inclusive, of theidrawings, includes, generally, a body l0, a plurality of vibratory neck I4 over which the strings IIare strung. In

accordance with the invention the neck I4 may be integral with thebody I0 and the instrument body may be a one-piece casting. The body I0 is preferably formed of a non-magnetic material such as aluminum or the like. The main portion of the body I0 may be of any suitable or convenient shape. In the particularcase illustrated the body.

III has a rounded or curved side I5, a fiat bottom I6 and a top I1 which is generally parallel with the bottom I6. The body I0 is preferably hollow or provided with an opening I8 whose walls may follow generally the sides I5, the bottom I6 and the top I1. The bottom I6 is in the form of a closure closing the lower end of the body opening I3. The bottom I6 may be secured to the body I0 by screws I9 or other suitable means. The neck I4 projects substantially radially from the body I0 and may be substantially rectangular in transverse cross section. A fingerboard 20 is provided on the upper side of the neck I4 and has the usual spaced frets 2|. A key-box portion or pegbox portion 22 is provided on the outer end of the neck I4. The body I0 and its'neck I4 may be` finished and ornamented as desired. The outer surface of the bottom I6 and the lower surface of the neck I4 are covered with felt 23, or the like. The felt 23 prevents the instrument fromsl'ipping on the musicians lap and protects his clothing. As'illustrated in Figs. 2` and 4 the edge portion of the felt 23 is received or recessed in a groove 8 in the lower edge portion of the body side I5. Fig. 9 illustrates a construction wherein The strings II are preferably arranged in parallelisml in a common plane suitably spaced above' the surfaces of the body and neck I4. In the particular instrument illustrated there are seven spaced substantially-parallel strings II, it being understood that the instrument may embody as many strings as desired or necessary. The strings II are graduated in diameter and some of them may be wound to produce the proper tones or vibrations. lIn accordance with the invention the strings II are of greater or less magnetic permeability than the air through which they pass. In practice, the strings II may be the usual steel strings commonly employed on guitars and similar instruments. Tensioning keys or pegs 22 are provided on the peg-box portion 22 and the outer end portions f the strings I I are wound upon the pegs. The body III is provided with a tail piece 24 and the strings II are arranged under tension between the tail piece 24 and the pegs 22.

The strings II pass through the slots 25 and the usual blocks or spools 26 on the strings cooperate with the rear side of the tail piece 24. The tensioned vibratory strings II engage or bear on a bridge 21 onithe body top I1. The bridge 21 may be secured in a slot 28 in an integral elevated portion of the top I1. In practice the bri\dge 21 may be spaced a short distance forwardlyfrom the tail piece 24. 'I'he body top I1 has an integral elevated portion I1UL through which the pole pieces of the pick-up unit project. It is to be noted that the tail piece 24, the bridge carrying portion, and the elevated portion I1a are integral parts of the rigid one-piece body I0. The strings IImay be tuned or tensioned by the pegs 22B, as desired. The particular instrument illustrated in the draw-4 ings is inthe nature of a steel guitar or Hawaiian guitar andthe strings I I are spaced a substantial distance above the ngerboard -20 and its -frets 2|.

The pick-up I2 is operable to convert the vibration of the strings II. into an electrical current which in turn may be converted linto sound or musical tones by a suitable amplifier and speaker circuit or unit 29. 'I'he pick-up I2 is inthe nature of an electromagnetic means providing a magnetic ileld through which the strings I I pass and is responsive to variations in the reluctance of said field caused by vibration of the strings. -The pick-up I2 includes a magnet 30. The magnet 30 is preferably in the nature of a permanent mag- `net whereby the pick-up I2 produces a minimum of hum. The magnet 30 is of the horse-shoe type having spaced substantially parallel arms 3| constituting the magnetic pole parts. The magnet 30 is arranged in the opening I8 of the body I0 and is preferably positioned so that its arms 3| are substantially horizontal and parallel with the strings II. It isa feature of the invention that the magnet 30 may be permanently or at least .rigidly mounted in the body I 0. 'I'he means for supporting or mounting the magnet -3|I may comprise a clamp plate 32 engaging against the lower sides of the magnet arms 3|. The plate 32 is preferably formed of non-magnetic material and is shaped to extend or i'lt between the arms 3| as best illustrated in Fig. 4 of the drawings. Screws\33 pass upwardly through openingsin the plate 32 and thread into openings 34 in a downwardly projecting box 35 on the under side of the top I1. The screws 33 bear upwardly against the plate 32 so that the magnet 30 is clamped upwardly against the under side,of the top I1.

The electro-magnetic pick-up I2 includes an induction coil C in the body I0'. The coil C comprises a form' or spool 36 and a winding 31 on the spool 36.v 'Ihe coil C islocated at or adjacent the pole ends of the magnet arms 3|. In accordance` with the invention the coil C may be rigidly secured to the'body I0. In the simple preferred arrangement illustrated, a recess 38 is provided in the underl surface of the body portionl I1 and the coil C is arranged within the recess 38. The upper end of the spool 36 is adapted to bear upwardly against the upper wall of the recess 38. 'I'he lower end of the coil spool 36v is engaged or clamped against the wall of the recess by the arms 3| of the magnet 30.

-The magnet 30 clamped or held upwardly by the plate 32, bears against the spool 36 to hold the spool in position. In accordance with the invention the coil spool 36 is elongated diametrically oi.' the axis of the winding 31 and the coil C is positioned so that the opposite end portions of the elongated spool extend laterally beyond ythe arms 3| of the magnet 30. An elongate opening or slot 39 extends vertically through the spool 3I5.` The slot 39 occurs at the pole ends of the magnet arms 3| and extends laterally or horizontally beyond the outer sides of the arms 3|. In practice the opposite ends of the elongated slot 39 are in planes spaced outwardly from the vertical planes of the outermost or end strings I I.

The improved electro-magnetic pick-up I2 oi' the invention includes pole pieces 4l for the magnet 30. The pole pieces arel flat plate-like parts. One pole piece 4|) engages against the pole end of eacharm 3| of the magnet 30. The inner opposing edges of the pole pieces 40 are preferably spaced apart and may be downwardly divergent. The pole pieces 4|) are formed of magnetic material and are held against the ends of the magnet arms 3| by the magnetic attraction.

The adjusting means |3 also operates to assist in holding the pole pieces 40 in cooperation with the magnet arms 3| as will be hereinafter described. The pole pieces 40 are provided to carry the magnetic circuit or iiux through the coil.C and to concentrate the magnetic field about the vibratory strings II. The pole pieces 40 extend upwardly or outwardly from the magnet arms 3| to project through the slot 33 in the coil spool 38. The pole pieces 40 thus form core elements of the coil C. A slot 4| is provided in the portion I'IL of the instrument body I0 in alignment and communication with the slot 39 and the upper end portions of the pole pieces 40 are adapted to extend through the slot 4I. The slots 39 and 4| are suiiiciently large to receive the pole pieces 40 with suitable clearance. In the preferred form of the invention the portion I'Iu of the top I1, provided with the recess 38 and the slot 4I, is eleva-ted so that the pole pieces 48 emerging from the slot 4| are adjacent the strings II as illustrated in Figs. 2 and 4 of the drawings. The pole pieces 40 are disposed transversely of the series of strings II and lie in a common plane substantially normal to the plane of the strings II. The pole pieces 40 are sufliciently wide to extend to or slightly beyond the end strings II and are sui'iiciently long to project downwardly` beyond the magnet arms 3| when projecting from the slot 4|. The upper edges 42 of the pole pieces 40 are preferably inclined downwardly from the inner edges of the pole pieces to the" outer edges of the pole pieces. The pole pieces 4|| are related to the strings II so that the space between the inner edges of the pole pieces is in a plane spaced between the longitudinal plane of two adjacent strings II. Where there are seven strings, as illustrated, one pole piece 40 is wider than the other to extend transversely below four of the strings II, while the said other pole pieceI is disposed transversely below three of the strings. This relationship is best illustrated in Fig. 4 of the drawings.

The pole pieces 40 engaging against the ends of the magnet arms 3| carry the magnetic flux or circuit to their upper edges 42. These edges 42 have limited areas providing a transverse concentrated magnetic eld. The concentrated magnetic eld arches from the edge 42 of one pole piece to the edge 42 of the other pole piece.

. Thus the pole pieces 40 are related to the magnet netic eld they vary the reluctance of the magnetic field space about them regardless oi the direction of such vibration. The magnet arms 3| and the pole pieces 40 are related so that the pole ends of the arms 3| are substantially equally spaced between the vertical edges of their respective pole pieces 40.

The means I3 for adjusting the pick-up I2 supports the pole pieces 40 for manual adjustment relative to the series of strings Il to vary the spaces between the edges 42 of the pole pieces of the strings and thus vary the action of the pick-up I2. The adjusting means i3 includes a shiftable carrier member 43 arranged substantially horizontally in the body opening i. 'Ii-ie carrier member 43 carries the pole pieces td for adjustment relative to the relatively stationary magnet 30 and strings II. 'I'he carrier member 43 is elongate and its end portions may curve rearwardly. 'I'he member 43 is disposed transversely of the series of strings Ii. The intermediate or middle portion of the member 43 is preferably broadened vertically to carry the plate-like pole pieces 40. It-is preferred to form the member 43 of non-magnetic material. Bolts or screws 44 secure the pole pieces iii to the rear side of the member 43. Spring means may be provided to assist the action of. the magnetic attraction in holding the pole pieces 4E in proper e full cooperation with the pole ends of the magnet arms 3|. An opening 45 is provided in the middle portion oi' the member 43 and a pin 46 extends through the opening 45. An extensible coiled spring 41 has one end connected with the pin 46 and its other end connected with one oi' the screws 33; The spring 41 is under tension -and urges the member 43 rearwardly to hold the rearsurfaces of the pole pieces 40 in even contact with the fiat ends of the magnet arms 3|.

In accordance with the invention the carrier mem-ber 43 of the adjusting means I3 is adjustably supported at its opposite ends for even vertical adjustment throughout its length or for adjustment from one end or both ends individually.

The means for adjustably supporting the member 43 and the pole pieces 40 carried thereby includes screws 48 threaded through openings 49 in the opposite end portions of the member. The screws 48 extend outwardly or upwardly to shiftably pass through openings 50 in the top I'I. The portions of the screws 48 passing through the openings 50 are preferably smooth and unthreaded so that `the screws may readily shift through the openings with suitable clearance. Heads 5| are provided on the outer ends of the screws 48 and are adapted to bear or react against the upper surface of the top I1. The screw heads 5| are preferably knurled for easy manual turning. Helical springs 52 surround the screws 48 and are arranged under compressure lbetween the member 43 and the top I 1. The springs 52 act downwardly on the member 43 to hold the screw heads 5| in engagement with the body top II so that threading of the screws 48 in either direction results in shifting of the member 43. The screws 48 may be simultaneously adjusted to shift the pole pieces 40 uniformly toward or away from the strings II or only one screw 48 may be adjusted or one screw 48 may be adjusted more rapidly than or in the opposite direction to the other to effect the desired unequal spacing of the pole piece edges 42 fromv the strings II. The screws 48 may be turned or adjusted in opposite directions to effect the unequal spacing of the edges 42 from the strings II or to equalize the spacing of the edges from the strings when the pole pieces have beenin non-uniform position-s.

Conductors 52 in the body opening lI8 are connected with the terminals of the winding 31 and extend to a receptacle or socket 53 in the rear wall of the body I6. A jack or plug 54 is adapted to be inserted in the socket 53. Leads or Acon'- ductors 55 extend from the plug 54 to the loudl speaker unit 29. Iny the drawings I have shown a typical amplifying or loud speaker circuit or unit 29, it being understood that the sound producing and amplifying apparatus shown is merely typical of the class of apparatus that may be employed with the invention. It is to be understood that the sound producing and amplifying unit 29 may be at a suitable remote point. The invention preferably includes a volume control 56 and a tone control 51 suitably connected in the leads or conductors 52. The volume control 56 and the tone control 51 are arranged'in the body opening I8 and may be readily governed or regulated by suitable knobs 56 and 51 projecting from the upper surface of the body top I1.

When the instrument is to be played the musician may adjust the volume control 56 and the tone control 51 to his liking. The pick-up unit I2 may be adjusted by manually turning the knobs or heads 5| of the screws 48. As above described, the 'screws 46 may be turned to shift the pole pieces 46 uniformly toward or away from the strings II or to bring the edge 42 of one pole piece 46 closer to the strings than the edge 42 of the other pole piece. In this manner the ac- I tion of the pick-up means I2 may be governed or regulated by the musician to change the tone of the instrument as a whole or to render the tones of either the higher or the lower strings more brilliant, as desired. `The pole pieces 46- of the pick-up provide a concentrated arched or non-uniform magnetic field through which vthe strings Ilpass. Vibration of the strings II va ries the reluctance of the magnetic field space about the strings to induce a current in the coil C. It will be apparent that the pole pieces 46 extending through the spool coil 36 link the magnetic flux or circuit with fthe winding 31 of the induction coil C. The vibration of one or more strings `II in the non-uniform concentrated magnetic field at the upper edges of the pole pieces 40 varies the reluctance of the magnetic flux or circuit. Variation of the reluctance of this magnetic circuit or flux linked with the coil winding y 31 sets up or induces an electrical circuit in the winding. This electrical current is carried lto the -speaker unit 29 where it is converted into musical representative of the actual sound producing vibration of the strings i I. The tones produced by the speaker of the instrument are clear musical tones free of crackle, hum and other noise, and are sustained -bya stringed instrument of the guitar type. It isl to -be noted that the pick-up I2 does not involve any parts touching the strings II or obtaining vibration of the strings by mechanical means. The pole pieces 46 may be easily and conveniently adjusted manually at any time without disturbing or shifting the magnet 36 or the induction coil C.

Figs. 6, 'l and 8 of the drawings illustrate the invention embodied inan instrument having a wooden body 66. The instrument illustrated in Figs. 6, 7 and 8 is of the guitar type andthe body 66 involves the usual sound box 6I and neck 82. v

Tensioned vibrator-y strings II* extend over the neck 62 and the sound box 6I. The construction of the sound box 6| and the neck 62, andthe manner of supporting and tensioning the strings Il may be typical. The invention provides an improved pick-up I2n and means 'I3 for regulating the pick-up I 2'.

IThe'pick-up l2" includes a bracket 63 carried by the Asound box 6I of the instrument body 66. The bracket 63 is substantially T-shaped having its majorv pant disposed transversely under the strings IIn and having a part 64 extending rearwardly and'substantially longitudinally of the strings. The bracket 63 is preferably formed of non-magnet material. An opening 65 in the sound box 6I is provided under the bracket 63 and may be of substantially the same shape as the bracket. The lower surface of the bracket 63 may bear on the top of the sound box 6I along the edge of the opening 65 and the bracket 63 may -be secured to the sound box by screws 66 or the like. The bracket 63 is provided with a part 61 which projects upwardly or outwardly toward the strings Il. The elevated part 61 is elongate and is disposed transversely of the strings IIB. A recess 68 occurs in the under side of the bracket part 61.

The pick-up I2Il includes a permanent magnet Y 69. The magnet 69 may be identical with the above described magnet 30. The magnet 69 is arranged within the sound box 36 in a substantially horizontal position where its arms 16 extend in substantially the same direction as the strings I I. The magnet 69 is secured or clamped to the bracket 63. Spaced lugs or bosses 1I are provided on the under side of the bracket and the upper side of the magnet 69 bears on these bosses 1I. A clamp plate 12 of non-magnetic material engages against the lower sidesof the magnet arms 16. Screws 13 extend through openings in the clamp plate 12 and thread into .openings 14 in the bracket 63. The screws 13 operate to clamp the magnet 69 upwardly against the bosses 1 i.

The improved pick-up I2 includes an induction coil C1 arranged in the recess 68. The coil Cl includes a spool 15 of insulating material and a winding 16 of suitable wire. The spool'15 is horizontally elongated and is arranged in the recess 68 so that its principal horizontal axis is substantiallytransverse of the direction of the strings IIB. The upper end ofthe spool 15 bears against the upper` wall of the recess 68. The upper surfaces of the magnet arms 10 bear against the lower side of the spool 15 to clamp thespool in the recess 69 and thus hold'the spoo in position. l

Magnetic pole pieces 11 are included in the pick-up l2. The pole pieces 11 are flat platelike members bearing against the pole ends of the magnet arms 16. A slot 18 is provided in the spool 15 and the pole pieces 11 project upwardly .through the slot 18. A slot 19 is provided in the bracket part 61 to register with the slot 18. The pole pieces 11 are adapted to project through the slot 19 to have their upper edges 86 adjacent the strings Il. The pole pieces 11 are disposed transversely of the strings Il,a and engage against the magnet arms 16 to provide an arched or non-uniform magnetic eld through which the strings Il pass. The inner edges of the pole pieces 11 are spaced apart and may be downwardly divergent. y

The means I3* for adjusting the pick-up I2s is manually operable to shift the pole pieces 11 to vary the spacing of their edges from the strings Ile. 'I'he adjusting means I3a includes a carrier member 8| arranged in the sound box 6I at the under side of the bracket 63. Screws 82 secure the pole pieces I'I to the member 8|. A spring 83 isconnected with the member 8| to urge the pole pieces Tl into proper contact with the pole ends of the arms 10. Adjusting screws 84 are threaded through openings in the opposite end portions of the member 8| and extend upwardly through openings 85 in the bracket 63. Knobs or knurled heads 86 are provided on the projecting upper ends of the screws 84. Springs 81 surround the screws 84 and are arranged under compression between the bracket 63 and the member 8|. Turning of the screws 84 effects shifting of the member 8| to adjust the pole pieces 'II relative to the vibratory strings IIE. The member 8| may be readily adjusted to space the edge 80 of one pole piece I1 closer or farther away from ythe strings than the edge 80 of the other pole piece.

Conductors or leads 88 extend from the terminals of the winding 16 to a receptacle or socket 89 in the wall of the sound box 6I. A suitable volume control 90 and a tone control 9| may be properly connected in the leads 88. The controls 90 and 9| may have handles or knobs projecting from the sound box 1| whereby they may be readily adjusted or controlled by the musician. Conductors (not shown) may be plugged into the socket 89 to connect the pick-up I 2a with an amplifier or loud speaker unit.` In practice the loud speaker unit may be similar to the unit 29 employed with the previously described form of the invention.

The pick-up I2a of the instrument illustrated in Figs. 6 to 8, inclusive, of the drawings operates in the same manner as the pick-up I2. The pick-up I2a may be easily and conveniently adjusted by lmeans of the screws 84 to have the desired action. The unit or pick-up I2 may be readily embodied in an .instrument having a wooden body or sound box with a minimum of alteration and modification. The principal parts of the pick-up I2 and its control or adjusting means I3a are enclosed within the sound box 6|.

Having described only typical preferred forms and applications of my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims.

Having described my invention, I claim:

1. In a pick-up for use on a musical instrument having a vibratory string, the combination of, a relatively stationary magnet on `the instrument, a relatively stationary induction coil, shiftable magnet pole pieces engaging the magnetand extending through the coil to provide a concentrated magnetic field about the string, and means for shifting the pole pieces.

2. A pick-up for a musical instrument having a vibratory string, the pick-up including a stationary horseshoe magnet, anl induction coil, pole pieces shiftable relative to the magnet and coil engaging the poles of the magnet and extending through the coil toward the string to provide a magnetic field through which the string passes, and means for shifting the pole pieces relative to the magnet and string.

3.' A pick-up for use on a musical instrument having a body and vibratory strings on the body,

the pick-up including a magnet, an induction coil, a pole piece engaging each pole of the magnet and extending through the coil toward the magnet to provide a magnetic field at the strings, the pole pieces being shiftable relative to the magnet, coil and strings,g and means for shifting the pole pieces relative to the magnet and strings to vary the spacing oi' the strings and pole pieces.

4. A pick-up for a musical instrument having a vibratory string comprising, a stationary magnet, an induction winding, members shiftable relative to the string and magnet engaging the `pole portions of the magnet and extending through the winding to have ends adjacent the string, and means operableto shift the members relative to the magnet and string to vary the magnetic field space between the said ends and the string, said means including, a shiftable part carrying the members, and screw means for shifting the part.

5. A pick-up for a musical instrument having vibratory strings comprising, a stationary magnet, an induction winding, pole pieces movable relative to the strings and magnet engaging the pole portions of the magnet and extending through the winding to have ends adjacent the strings, said pole pieces being transverse of the strings and providing a magnetic field about the strings, and means for shifting the pole pieces through the winding to vary the magnetic field spaces between their ends and the strings including a movable member connected with the pole pieces, and manually operable means for moving said member.

6. A pick-up for use on a musical instrument having a series of spaced vibratory strings, the

pick-up including a stationary permanent magnet, movable pole pieces disposed transversely of the series of strings and cooperating with the pole portions of the magnet, the pole pieces having surfaces of limited area spaced from the strings providing a concentrated magnetic field space through which the strings pass, an induction -coil surrounding the pole pieces, and means supporting the pole pieces and operable to move the pole pieces relative to the magnet to vary the field spaces between the strings and the said surfaces.

7. A pick-up for use on a musical instrument having a series of spaced vibratory strings, the pick-up including a stationary permanent magnet, movable pole pieces disposed transversely of the series of strings and cooperating with the pole portions of the magnet, the pole pieces having surfaces spaced from the strings to provide a magnetic field around the strings, a tiltable carrier carrying the pole pieces,`and manually operable adjusting means for tilting the carrier to vary the spaces between the strings and said surfaces.

8. A pick-up for use on a musical instrument having a series of spaced vibratory strings, the pick-up including a stationary permanent magnet, movable pole pieces disposed transversely of the series of strings and cooperating with the pole portions of the magnet, the pole pieces having surfaces spaced from the strings to provide a magnetic field around the strings, a carrier carrying the pole pieces, and spaced screws carrying the carrier and the pole pieces thereon for adjustment relative to the strings whereby the spaces between the strings and said surfaces may be varied.

9. A pick-up for use on a musical instrument having a series of spaced vibratory strings, the

10. In a pick-up for use on a 'musical instru- -ment having a series of spaced vibratory strings,

the pick-upincluding a stationary permanent magnet, movable pole pieces disposed transversely of the series of strings and cooperating with the pole portions of the magnet, the pole pieces having surfaces spaced from thestrings to provide'a magnetic neld around the strings,

a movable carrier carrying the pole pieces and arranged transversely of the series of strings. y.

andmanually adjustable screws supporting the opposite ends of the carrier for adjustment whereby the spaces between the strings and said surfaces may be varied.

11. lA pick-up forv use on -a musical instrument havinga series of spaced vibratory strings, the pick-up including a stationary magnet, movable magnetic plate members cooperating with the pole portions of the magnet and extending toward the strings, the memberslying in a plane transverse of the strings and each having an edge surface spaced from a number of adjacent strings to provide a magnetic iield at the strings, an induction winding around the members, and means for adjusting the members bodily toward and away from the strings and for tilting'the net, movable pole pieces disposed transversely of the series of strings and shiftably cooperating with the pole portions of the magnet, the pole pieces having surfaces -of limited area spaced from the strings providing a concentrated magnetic field space through which the strings pass.

an induction coil surrounding the pole pieces,

means holding the movable polepieces in coop'- eration with the pole portions of the stationary magnet, and means for moving the pole pieces relative to the magnet to vary the field spaces between the strings and the said surfaces comprising a 'carrier for the pole pieces, and screws for shifting the carrier. l

13. A pick-up for use on a musical instrument having a series of spaced'vibratory strings, the pick-up including a stationary magnet, movable magnetic plate members cooperating with the pole portions of the magnet 'and extending toward the strings, the members lying in a plane transverse of the strings and each having an edge surface spaced from a. number of adjacent strings to-provide a magnetic eld at the strings, an induction winding around the members, a movable carrier carrying the members, and means supporting the carrier for bodily movement and tilting movement operable to vary vthe spacing of said surfaces and the adjacent strings.

RUDoLH noPYERA. 

